The present invention relates to a diagnostic indirect ophthalmoscopy contact lens device. More particularly, the invention relates to a diagnostic contact lens for indirect ophthalmoscopy which operates both as an improved condensing lens device for conveyance of a light through the pupil and onto the fundus of an examined eye as well as for forming a aberration free and extremely wide field inverted real aerial image of the fundus of the eye.
Diagnostic lenses for indirect ophthalmoscopy are used by ophthalmologists and optometrists to observe the fundus of an eye for diagnostic or surgical procedures. Various known ophthalmoscopic lenses or other diagnostic devices, have lenses for conveying light from a source onto the fundus of an eye and forming an aerial image of the fundus. In U.S. Pat. No. 3,954,329, there is shown an ophthalmoscope for viewing a fundus which includes a contact lens which directly contacts the cornea of the eye as well as a posterior or field lens spaced from the contact lens and supported in a housing relative thereto. This invention employs both direct illumination of the fundus of the eye as well as transillumination to obtain wide angle viewing of the fundus. Other similar systems in U.S. Pat. Nos. 4,265,519 and 3,994,341 show various illumination techniques and lens systems for ophthalmoscopes and fundus cameras.
More recently, indirect ophthalmoscopy has been utilized in laser microsurgery techniques to enable the ophthalmologists to obtain a wide angle image of the fundus as well as to convey the laser beam to the fundus accurately. In an attempt to provide wide angle viewing of the fundus without aberration, U.S. Pat. No. 4,728,182 to Heacock utilizes a contact lens element situated relative to an entry lens in a holder. It is stated that the contact lens element is designed such that the light rays emerging from the patient's eye exit the contact lens in a parallel relationship which are then directed to the entry lens. The entry lens is an aspheric lens which forms an aerial image of the fundus.
This patent thus describes an ophthalmic lens system wherein the contact lens has two spherical surfaces, designed such that light rays emerging from the patient's eye and through the contact lens are substantially parallel, rather than convergent, as they exit in an anterior direction from the contact lens. In this design, the aspheric entry lens of this invention will be inadequate in some circumstances as an image forming lens as it will be insufficient for correcting field curvature and aberrations due in part to the spherical design of the contact lens. The contact lens design has failed to account for the corrective quality of the aspheric cornea of the eye itself and may tend to degrade the image of the fundus of the eye.
It is also desired to form an extremely wide field image of the fundus of the eye using a diagnostic contact lens system to enable the ophthalmologist and optometrist to view more of the fundus for proper and easier diagnosis. In the invention of Heacock as well as other prior art inventions, mirrors are sometimes interposed between the contact lens and entry lens of the system to increase the field of view of the fundus. The addition of mirrors into the system adds complexity, costs and may tend to degrade the quality of the image. Even with the use of mirrors it may still be necessary to move the lens on the examined eye.
In a similar manner, the indirect ophthalmoscopy diagnostic contact lens system should function as a condensing lens for converging light from the light source of a biomicroscope through the pupil of an examined eye onto the fundus of the eye. In order to obtain an aberration free, focused image of the light source, such as in a slit lamp biomicroscope or other ophthalmoscope, the lens system should provide the optical properties to avoid aberrations normally associated with spherical lenses.